1,2,3‐ and 1,2,4‐triazolium salts,pyrazoles, and quinoxalines from diarylnitrilimines and isocyanides: A study of the scope

Formation of the four title compounds has been found to be strongly dependent on substituents: 1,2,3‐Triazolium salts 6 do not arise from nitrilimines 2 that have an electron‐acceptor attached to either the C‐ or the N‐phenyl group. Likewise tert‐butyl and aryl isocyanides do not afford this class of compounds; from the former isocyanide, dequaternization products 7 are obtained instead, whereas from the latter 1,2,4‐triazolium salts 11 are formed. Compounds 11 with tert‐butyl group at the ring are unstable too, giving rise to triazoles 13 . Pyrazole formation (analogues of 14 ) is completely suppressed when both tert‐butyl and aryl isocyanides are used, whereas access to this ring system works best with see‐alkyl isocyanides (the influence of substituents of 2 being almost negligible in this case). Formation of quinoxalines 23 which arise from intermediary 1,2‐diazets 22 by ring expansion is much favoured on employment of 2 that bears a donator substituent at the N‐phenyl group, and under this premise ring closure to 22 is virtually independent on the nature of the isocyanide. Formation of 23 is not observed with 2 having acceptor groups.